The Commodore is a classic cocktail with a bewildering variety of suggested recipes. Some have not a single ingredient in common, which are obviously no longer variations but completely different drinks. As near as I can tell, this is the original recipe from The Old Waldorf-Astoria Bar Book:

2 oz Bacardi rum

1 egg white

1/2 tsp sugar

dash of lemon juice

dash of grenadine

dash of raspberry syrup or liqueur

As with any drink incorporating eggs, I'd recommend my new trick of breaking up the albumen first before adding whites to the rest of the ingredients. If you don't have a pestle then a whisk will do the job nicely. Shake well, and strain into a martini glass.